1. Field of the Invention
The present invention relates to a technique for controlling a resolution in an image processing system, and more particularly a technique for automatically controlling a resolution of a document to be transmitted and/or copied.
2. Description of the Related Art
In general, a facsimile has a resolution control function which includes a standard mode, a fine mode, and a super fine mode. If a user selects one of the above mentioned resolution modes by using an operating panel in order to control a resolution of the document to be transmitted, a controller (e.g., central processing unit) recognizes the selected resolution mode and transmits corresponding mode information according to a protocol to a called facsimile prior to transmitting actual image data. Thereafter, the facsimile transmits the document image based on the selected mode information. At this moment, the user should check every new page as to whether or not the resolution mode should be changed, thereby causing inconveniences. Once the resolution mode is selected for a page, the whole page will be transmitted with the same resolution.
The standard mode is to scan the document every other line (where one line is 1/7.7 mm) and code the scanned image to transmit to the called facsimile. Then, the called facsimile prints one line with the received image and prints a next line with the same image. The fine mode is to scan the document line by line and code the scanned image to transmit to the called facsimile. Then, the called facsimile prints the received images line by line. Further, the super fine mode is to scan the document every half line (where a half line is 1/15.4 mm) and code the scanned image to transmit to the called facsimile. The transmitted image is printed at the called facsimile every half line. Thus, in the light of the vertical lines, the resolution with respect to one line becomes 1/3.85 mm in the standard mode, 1/7.7 mm in the fine mode, and 1/15.4 mm in the super fine mode. For the convenience of explanation, it is assumed that one line is 1/7.7 mm throughout the specification.
As can be clearly appreciated from the above descriptions, the standard mode has a fast transmission speed but a low resolution. On the contrary, the fine mode and the super fine mode have a high resolution, but they have the disadvantage of the low transmission speed. Conventionally, when scanning a document in a facsimile, the user should determine an elaboration of the document by the naked eye, and select the resolution mode accordingly.
Therefore, in the case where the document is a mixture of the elaborative image and the normal image, several problems may be caused unavoidably. Namely, it takes a long time to transmit the document in the fine or super fine mode continuously, which results into an expensive communication fee. On the contrary, if the user transmits the document in the standard mode in order to reduce the transmission time, a quality of the image will be degraded. Furthermore, in the case where the facsimile is erroneously set to the standard mode for a document that should have been set to the fine or super fine mode, the user might retransmit document due to the degradation of the image.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited features of the present invention: U.S. Pat. No. 5,337,159 to Iida et al., entitled Image Data Smoothing Method, U.S. Pat. No. 5,274,462 to Satoh, entitled Image Input And Output Method, U.S. Pat. No. 4,028,731 to Arps et al., entitled Apparatus For Compression Coding Using Cross-Array Correlation Between Two-Dimensional Matrices Derived From Two-Valued Digital Images, U.S. Pat. No. 4,070,694 to Sakamoto et al., entitled Picture Image Information Band Compression And Transmission System, U.S. Pat. No. 4,115,815 to Nakagome et al., entitled Facsimile Signal Coding Method, U.S. Pat. No. 4,191,974 to Ono et al., entitled Facsimile Encoding Communication System, U.S. Pat. No. 3,974,325 to Wilmer, entitled Interpolator For Facsimile Bandwidth Compression, U.S. Pat. No. 4,193,092 to Stoffel, entitled Image Interpolation System, U.S. Pat. No. 4,291,339 to Ogawa et al., entitled Facsimile Transceiver, U.S. Pat. No. 4,396,952 to Tisue et al., entitled Facsimile Transmission Apparatus, and U.S. Pat. No. 4,571,632 to Schaphorst et al., entitled Alternate Line Interpolation Method And Apparatus.